The present invention relates generally to pressure cookers and more particularly to a pressure cooker cover interlock. The interlock prevents pressurizing the pressure cooker if the cover is not completely closed and the interlock prevents opening the cover if the pressure cooker is pressurized.
This invention includes a locking device which prevents a build up of pressure when the cover is not securely locked onto the pressure cooker body. This locking device also prevents removal of the cover when the pressure inside the pressure cooker body is greater than 1 p.s.i. The interlock function is a valuable feature since it may prevent improper use of the pressure cooker. This interlock also, exhibits a simplified design which results in reduced manufacturing costs.
The prior art, reflected by U.S. Pat. No. 4,620,643, to Sebillotte teaches a thumb-actuated locking device which cooperates with a valve stem in the lid to prevent closure of the valve when the two handles are not in a "locked position." This locking device also prevents opening of the lid when the valve is in a "closed position." The locking device consists of a push rod mounted in the handle of the lid, which locks the two handle portions together when the vessel is pressurized. The valve stem enters the hole of the locking member when the two handles are in the locked position, and the vessel is under pressure. The lid may be opened after the pressure in the vessel drops and the valve stem drops out of the hole. The control button is then pushed to disengage the push-rod from a locking recess in the lower handle.
French Patent No. 2,484,817, filed May 11 1979, also shows a pressure-activated interlock system which uses a thumb-switch to retract a lock mechanism.
Walker et al. U.S. Pat. No. 4,162,741, also describes a pressure-activated interlock. A pressure operated plunger located in the cover cooperates with a tab or abutment mounted inside the body of the cooker. This interlock inhibits the removal of the cover when the cooker is pressurized and prevents pressure build up in the vessel when the cover is incompletely locked to the body. This locking device consists of a cylindrical stem located within the cover and a horizontal abutment located on the interior wall of the vessel. The stem hangs from an opening in the cover when the vessel is unpressurized the catch portion of the stem hangs below the abutment and is free to pass beneath it. If the cover is not rotated far enough to completely lock it to the body, as the stem rises with increasing pressure inside the vessel and the catch portion catches on the underside of the abutment preventing the sealing of the opening. This action prevents pressurization of the cooker. However, if the cover is properly positioned on the body, the catch portion rotates clear of the abutment and rises with increasing pressure to seal the opening, thus permitting pressurization. While in the sealed position, rotation of the cover is prevented by the catch portion which is now located side by side with the abutment.